Appropriation is the legal means by which land held by a local authority is transferred from one legal function to another. Much like the purchase of land (compulsorily or by agreement) for certain statutory purposes, e.g. planning purposes, the process will have the effect of overriding rights (subject to the payment of compensation) that affect the land, e.g. restrictive covenants etc. It is therefore an important issue.
It is also often critical for local authorities when defending (as the landowner) town or village green applications. It also arises in other circumstances, such as in the recent High Court decision (9 November 2018) in Ramsgate Town Council v Thanet District Council  EWHC 3042 (Ch). Appropriation was the focus of a dispute over which of two local authorities owned some land. The case arose out of a statutory order that effectively declared that land held by Thanet District Council for allotment purposes as of 1 April 2009 would be automatically transferred to Ramsgate Town Council.
The Court observed that there are no statutory formalities required for an effective appropriation and concluded that appropriation, as a matter of law, comes into effect when a local authority formally records that it has made the decision to appropriate or where (as in this case) it needs further consents before the appropriation may come into effect, e.g. the consent of the Secretary of State, when those further consents have been received.
The Court's approach here is reinforced by the decisions in R (Goodman) v SSEFRA  which in turn cites the unreported case of Oxy-Electric Ltd v Zainuddin .
This is a clarification of the law that local government property lawyers will particularly welcome.
Since there are no statutory formalities required for an effective appropriation, such an appropriation ought sensibly to be regarded as having been made when the Defendant put on formal record its intention to behave henceforth in a particular way, and seeks the necessary consents to enable it to do so legitimately. Once those consents have been received, the appropriation of the Land to another use is effective unless the imposed conditions make other provision, e.g. for continued use as allotment land for a further period before the consent to another use is effective.